Adhesive materials or filling materials are used for restorative treatment of teeth, bones, etc. Polymerizable compositions containing a polymerizable monomer, a polymerization initiator, a filler, etc., are generally used as such adhesive materials or filling materials. Polymerizable compositions for restorative treatment of teeth, bones, etc., can be roughly classified into two types depending on the hardness after curing. One type is a soft material, a cured product of which is flexible, to be used as an adhesive material, a shock absorber, etc., with respect to biological tissues, such as a temporary sealing material, a rebase for denture base, and an artificial cartilage. With the recent development of dental care, there is a glowing demand for new soft materials.
For example, dental treatment by implantation is widely used in recent years for the patients who have lost their teeth due to aging, etc. An implant is composed of an artificial tooth root to be embedded directly in the jaw bone, a tooth crown to be placed thereabove, and a tooth base, called an abutment, which engages the artificial tooth root and the tooth crown. These parts are bonded together at the time of use. For the bonding, a temporary cement is used, but the bonded portion is required to be removable because the implant occasionally needs to be detached for maintenance such as washing. Therefore, a cured product of the temporary cement is required to have excellent flexibility. The temporary cement also is required to have appropriate viscosity and forming property before curing so as to have excellent handling property. Further, it is required to have good adhesive properties with respect to metals and ceramics.
Meanwhile, the growth of periodontal disease causes gingival recession also due to aging, etc., making it difficult to support teeth sufficiently. As a result, the teeth become loose and lost easily. These loose teeth are called mobile teeth. To treat such a mobile tooth, a method of fixing the mobile tooth to a sound tooth using a mobile tooth-fixing material is employed. The mobile tooth-fixing material needs to be removed after recovery, and thus is required to be removable. It also is required not to break due to bending distortion to be applied continuously during the fixing until recovery. For this reason, a cured product of the mobile tooth-fixing material is required to have excellent flexibility. The mobile tooth-fixing material also is required to have appropriate viscosity and forming property before curing so as to have excellent handling property. Further, it also is required to have good adhesive properties with respect to tooth structure. Furthermore, a cured product thereof is required to have excellent transparency and color stability from the viewpoint of the aesthetic value.
As a method for imparting flexibility to a polymerizable composition, it is known to add an elastomer. For example, Patent Literature 1 reports an example in which the impact resistance of a metallic color-shielding adhesive material set for dental use is improved by adding butadiene-methyl methacrylate-styrene copolymer powder, thereby imparting flexibility thereto. Further, Patent Literatures 2 to 4 report examples in which a dental composition to be used for denture base, etc., is made flexible by adding a styrene-diene block copolymer thereto, so that the stress relaxation properties and the adhesive properties to the denture base are improved. Further, Patent Literature 5 reports an example in which the long-term coloration/discoloration and water absorption properties of a dental coating material composition are improved by adding a styrene-based thermoplastic elastomer or a methyl methacrylate-butyl acrylate copolymer thereto.